Lungs of individuals with cystic fibrosis (CF) are frequently colonized with a number of bacterial pathogens. One of the most common organisms is Pseudomonas aeruginosa. Previous studies have shown the presence of the type III-secretion pathway within P. aeruginosa, implicating these cytotoxins as virulence factors for this organism. To evaluate further the effect of these cytotoxins on lung cells, we would like to collect plasma and tissue from individuals with CF. Because larger quantities of plasma than can safely be obtained by simple phlebotomy will be required, apheresis procedures performed in the Clinical Center Apheresis Unit will be used. To obtain lung cells from patients with CF infected with P. aeruginosa, tissue from explanted lungs will be collected in collaboration with INOVA Fairfax Hospital. We intend to look for expression of the type- III proteins of P. aeruginosa by measuring the immune response against components of the type- III pathway and their presence in lung cells.